Microreactors based on zeolites and related materials are one of the latest developments in the field which started with the use of crystalline alumino-silicates for catalysis in the 1960s. These crystalline materials are highly thermally and hydrothermally stable, the number and strength of their acid sites can be controlled, they have a high adsorption capacity, and contain channels of molecular dimensions, properties of interest for a number of applications. The history of the field is traced and a number of new applications of these materials is reviewed.